1. Field of the Invention
This invention pertains generally to electric pumps. More specifically, this invention pertains to an electric pump that comprises a novel endshield.
2. General Background
Electric fluid pumps, such as those used in appliances, often comprise a centrifugal fluid pump attached to one end of an electric motor. Typically, the centrifugal pump comprises an impeller that rotates in a volute. The impeller is rotationally driven by the rotor of an electric motor and the volute is typically fastened to the adjacent endshield of the electric motor. One or more seals typically inhibit water or other fluids from traveling along or around the rotor shaft to the core of the electric motor's stator. However, over time and as the pump wears, it is not uncommon for at least some fluid to migrate past the seal or seals. Fluid seepage that migrates into an adjacent electric motor can negatively impact the efficient operation of the motor or shorten its useful life. For these reasons, the electric motor and pump are typically oriented relative to each other in a manner such that the electric motor is not directly beneath the pump. Thus it is often desirable to position the electric motor and the pump side-by-side. While positioning the electric motor to the side, rather than beneath the pump, inhibits seepage into the motor, liquid seepage from the pump bearings still may nonetheless travel along or around the rotor shaft toward the stator.
In view of these concerns, it is known to provide an electric pump with a liquid drainage cavity that is specifically configured to prevent liquid that has seeped past the rotor shaft bearing of the pump from being drawn by capillary action into the stator of the electric motor. The cavity is typically formed in the interface plate of the electric motor and encircles the rotor shaft in a manner providing an annular void around a portion of the shaft. The cavity thereby provides a place for seeped liquid to migrate and prevents capillary action from drawing the liquid into the stator, which would likely occur if there was little space around the shaft. Assuming the liquid seepage is slight, the cavity can serve as a reservoir for such liquid and thereby prevent the liquid from migrating into the stator. However, if the seepage is too great, the fluid will fill the cavity and then migrate into the stator. For this reason, some electric pumps comprise a drainage passageway configured to drain the cavity.
In addition to the concerns discussed above, there is also an endless desire to minimize the size of electric pumps without compromising their performance. The incorporation of a cavity for draining fluid seepage typically increases the overall length of an electric pump and therefore can be undesirable.